Practical Approaches to Adaptive Resource Allocation in OFDM Systems

Whenever a communication system operates in a time-frequency dispersive radio channel, the link adaptation provides a benefit in terms of any system performance metric by employing time, frequency, and, in case of multiple users, multi-user diversities. With respect to an Orthogonal Frequency Division Multiplexing (OFDM) system, link adaptation includes bit, power, and sub-carrier allocations. While the well-known water-filling principle provides the optimal solution for both margin-maximization and rate maximization problems, implementation complexity often makes difficult its application in practical systems.